The present invention relates to T helper cell epitopes derived from Canine Distemper Virus (CDV). The present invention relates to compositions including at least one T helper cell epitope and optionally B cell epitopes and/or CTL epitopes.
For any peptide to be able to induce an effective antibody response it must contain particular sequences of amino acids known as epitopes that are recognised by the immune system. In particular, for antibody responses, epitopes need to be recognised by specific immunoglobulin (Ig) receptors present on the surface of B lymphocytes. It is these cells which ultimately differentiate into plasma cells capable of producing antibody specific for that epitope. In addition to these B cell epitopes, the immunogen must also contain epitopes that are presented by antigen presenting cells (APC) to specific receptors present on helper T lymphocytes, the cells which are necessary to provide the signals required for the B cells to differentiate into antibody producing cells.
In the case of viral infections and in many cases of cancer, antibody is of limited benefit in recovery and the immune system responds with cytotoxic T cells (CTL) which are able to kill the virus-infected or cancer cell. Like helper T cells, CTL are first activated by interaction with APC bearing their specific peptide epitope presented on the surface, this time in association with MHC class I rather than class II molecules. Once activated the CTL can engage a target cell bearing the sane peptide/class I complex and cause its lysis. It is also becoming apparent that helper T cells play a role in this process; before the APC is capable of activating the CTL it must first receive signals from the helper T cell to upregulate the expression of the necessary costimulatory molecules.
Helper T cell epitopes are bound by molecules present on the surface of APCs that are coded by class II genes of the major histocompatibility complex (MHC). The complex of the class II molecule and peptide epitope is then recognised by specific T-cell receptors (TCR) on the surface of T helper lymphocytes. In this way the T cell, presented with an antigenic epitope in the context of an MHC molecule, can be activated and provide the necessary signals for the B lymphocyte to differentiate. Traditionally the source of helper T cell epitopes for a peptide immunogen is a carrier protein to which peptides are covalently coupled but this coupling procedure can introduce other problems such as modification of the antigenic determinant during the coupling process and the induction of antibodies against the carrier at the expense of antibodies which are directed toward the peptide (Schutze, M. P., Leclerc, C. Jolivet, M. Audibert, F. Chedid, L. Carrier-induced epitopic suppression, a major issue for future synthetic vaccines. J Immunol. 1985, 135, 2319-2322; DiJohn, D., Torrese, J. R. Murillo, J. Herrington, D. A. et al. Effect of priming with carrier on response to conjugate vaccine. The Lancet. 1989, 2, 1415-1416). Furthermore, the use of irrelevant proteins in the preparation introduces issues of quality control. The choice of appropriate carrier proteins is very important in designing peptide vaccines and their selection is limited by factors such as toxicity and feasibility of their large scale production. There are other limitations to this approach including the size of the peptide load that can be coupled and the dose of carrier that can be safely administered (Audibert, F. a. C., L. 1984. Modern approaches to vaccines. Molecular and chemical basis of virus virulence and immunogenicity., Cold Spring Harbor Laboratory, New York.). Although carrier molecules allow the induction of a strong immune response they are also associated with undesirable effects such as suppression of the anti-peptide antibody response (Herzenberg, L. A. and Tokuhisa, T. 1980. Carrier-priming leads to hapten-specific suppression. Nature 285:664; Schutze, M. P., Leclerc, C., Jolivet, M., Audibert, F., and Chedid, L. 1985. Carrier-induced epitopic suppression, a major issue for future synthetic vaccines. J Immunol 135:2319; Etlinger, H. M., Felix, A. M., Gillessen, D., Heimer, E. P., Just, M., Pink, J. R., Sinigaglia, F., Sturchler, D., Takacs, B., Trzeciak, A., and et, a. 1988. Assessment in humans of a synthetic peptide-based vaccine against the sporozoite stage of the human malaria parasite, Plasmodium falciparum. J Immunol 140:626).
In general then, an immunogen must contain epitopes capable of being recognised by helper T cells in addition to the epitopes that will be recognised by surface Ig or by the receptors present on cytotoxic T cells. It should be realised that these types of epitopes may be very different. For B cell epitopes, conformation is important as the B cell receptor binds directly to the native immunogen. In contrast, epitopes recognised by T cells are not dependent on conformational integrity of the epitope and consist of short sequences of approximately nine amino acids for CTL and slightly longer sequences, with less restriction on length, for helper T cells. The only requirements for these epitopes are that they can be accommodated in the binding cleft of the class I or class II molecule respectively and that the complex is then able to engage the T-cell receptor. The class II molecule""s binding site is open at both ends allowing a much greater variation in the length of the peptides bound (Brown, J. H., T. S. Jardetzky, J. C. Gorga, L. J. Stern, R. G. Urban, J. L. Strominger and D. C. Wiley. 1993. Three-dimensional structure of the human class II histocompatibility antigen HLA-DR1, Nature 364:33) with epitopes as short as 8 amino acid residues being reported (Fahrer, A. M., Geysen, H. M., White, D. O., Jackon, D. C. and Brown, L. E. Analysis of the requirements for class II-restricted T-cell recognition of a single determinant reveals considerable diversity in the T-cell response and degeneracy of peptide binding to I-Ed J. Immunol. 1995. 155: 2849-2857).
Canine distemper virus (CDV) belongs to the subgroup of morbillivirus of paramyxovirus family of negative-stranded RNA viruses. Other viruses which are members of this group are measles virus and rinderpest virus. Development of peptide based vaccines has aroused considerable interest in identification of B and T cell epitopes from sequences of proteins. The rationale for using T cell epitopes from proteins such as the F protein of CDV is that young dogs are inoculated against CDV in early life and will therefore possess helper T cells specific for helper T cell epitopes present on this protein. Subsequent exposure to a vaccine which contains one or more of the epitopes will therefore result in recruitment of existing helper T cells and consequently an enhanced immune response. Such helper T cell epitopes could, however, be administered to unprimed animals and still induce an immune response. The present inventors aimed to identify canine T cell epitopes from the sequence of CDV fusion protein so that these epitopes can then be used in the design of peptide based vaccines, in particular, for the canine and related species.
LHRH (Luteinisiing hormone releasing hormone) is a ten amino acids long peptide hormone whose sequence is conserved in mammals. It is secreted by the hypothalamus and controls the reproductive physiology of both males and females. The principle of development of LHRH-based immunocontraceptive vaccines is based on observations that antibodies to LHRH block the action of the hormone on pituitary secretion of luteinising hormone and follicle stimulating hormone, leading to gonadal atrophy and sterility in mammals.
Most LHRH vaccines that have been developed consist of LHRH chemically conjugated to protein carriers to provide T cell help for the generation of anti-LHRH antibodies. It has been shown that upon repeated inoculation of LHRH-protein carrier conjugates the anti-LHRH titre decreases due to the phenomenon known as xe2x80x9ccarrier induced epitope suppressionxe2x80x9d. One aim of the present inventors is to replace protein carriers in the vaccines with defined T helper epitopes (TH-epitopes) so as to eliminate xe2x80x9ccarrier induced epitope suppressionxe2x80x9d.
The present inventors have identified a number of 17 residue peptides each of which includes a T helper cell epitope. As will be readily appreciated the majority of these peptides are not minimal T helper cell epitopes. Typically class II molecules have been shown to be associated with peptides as short as 8 amino acids (Fahrer et al., 1995 ibid) but usually of 12-19 amino acids (Chicz, R. M., Urban, R. G., Gorga, J. C., Vignali, D. A. A., Lane, W. S. and Strominger, J. L. Specificity and promiscuity among naturally processed peptides bound to HLA-DR alleles, J Exp Med 1993, 178, 27-47; Chicz, R. M., Urban, R. G., Lane, W. S., Gorga, J. C., Stern, L. J., Vignali, D. A. A. and Strominger, J. L. Predominant naturally processed peptides bound to HLA-DR1 are derived from MHC-related molecules and are heterogeneous in size. Nature 1992, 358, 754-8), although, peptides up to 25 amino acids in length have been reported to bind to class II (reviewed in Rammensee, H.-G. Chemistry of peptide associated with class I and class II molecules. Curr Opin Immunol 1995, 7, 85-95.).
Thus peptide epitopes that range in length between 8 and 25 amino acid residues can bind to class II molecules. The shorter peptides are xe2x80x9ccorexe2x80x9d epitopes that may have less activity than longer sequences but it is a trivial exercise to truncate longer sequences at the N- or the C-terminus to yield shorter sequences that have the same or better activity than the parent sequence .
Accordingly in a first aspect the present invention consists in a T helper cell epitope, the epitope being contained within a peptide sequence selected from the group consisting of SSKTQTHTQQDRPPQPS (SEQ ID NO:1); QPSTELEETRTSRARHS (SEQ ID NO:2); RHSTTSAQRSTHYDPRT (SEQ ID NO:3); PRTSDRPVSYTMNRTRS (SEQ ID NO:4); TRSRKQTSHRLKNIPVH (SEQ ID NO:5); SHQYLVIKLIPNASLIE (SEQ ID NO:6); IGTDNVHYKIMTRPSHQ (SEQ ID NO:7); YKIMTRPSHQYLVIKLI (SEQ ID NO:8); KLIPNASLIENCTKAEL (SEQ ID NO:9); AELGEYEKLLNSVLEPI (SEQ ID NO:10); KLLNSVLEPINQALTLM (SEQ ID NO:11); EPINQALTLMTKNVKPL (SEQ ID NO:12); FAGVVLAGVALGVATAA (SEQ ID NO:13); GVALGVATAAQITAGIA (SEQ ID NO:14); TAAQITAGIALHQSNLN (SEQ ID NO:15); GIALHQSNLNAQAIQSL (SEQ ID NO:16); NLNAQAIQSLRTSLEQS (SEQ ID NO:17); QSLRTSLEQSNKAIEEI (SEQ ID NO:18); EQSNKAIEEIREATQET (SEQ ID NO:19); TELLSIFGPSLRDPISA (SEQ ID NO:20); PRYIATNGYLISNFDES (SEQ ID NO:21); CIRGDTSSCARTLVSGT (SEQ ID NO:22); DESSCVFVSESAICSQN (SEQ ID NO:23); TSTIINQSPDKLLTFIA (SEQ ID NO:24); SPDKLLTFIASDTCPLV (SEQ ID NO:25) and SGRRQRRFAGVVLAGVA (SEQ ID NO:26).
In a second aspect the present invention consists in a composition for use in raising an immune response in an animal, the composition comprising at least one T helper cell epitope, the at least one T helper cell epitope being contained within a peptide sequence selected from the group consisting of SSKTQTHTQQDRPPQPS (SEQ ID NO:1); QPSTELEETRTSRARHS (SEQ ID NO:2); RHSTTSAQRSTHYDPRT (SEQ ID NO:3); PRTSDRPVSYTMNRTRS (SEQ ID NO:4); TRSRKQTSHRLKNIPVH (SEQ ID NO:5); SHQYLVIKLIPNASLIE (SEQ ID NO:6); IGTDNVHYKIMTRPSHQ (SEQ ID NO:7); YKIMTRPSHQYLVIKLI (SEQ ID NO:8); KLIPNASLIENCTKAEL (SEQ ID NO:9); AELGEYEKLLNSVLEPI (SEQ ID NO:10); KLLNSVLEPINQALTLM (SEQ ID NO:11); EPINQALTLMTKNVKPL (SEQ ID NO:12); FAGVVLAGVALGVATAA (SEQ ID NO:13); GVALGVATAAQITAGIA (SEQ ID NO:14); TAAQITAGIALHQSNLN (SEQ ID NO:15); GIALHQSNLNAQAIQSL (SEQ ID NO:16); NLNAQAIQSLRTSLEQS (SEQ ID NO:17); QSLRTSLEQSNKAIEEI (SEQ ID NO:18); EQSNKAIEEIREATQET (SEQ ID NO:19); TELLSIFGPSLRDPISA (SEQ ID NO:20); PRYIATNGYLISNFDES (SEQ ID NO:21); CIRGDTSSCARTLVSGT (SEQ ID NO:22); DESSCVFVSESAICSQN (SEQ ID NO:23); TSTIINQSPDKLLTFIA (SEQ ID NO:24); SPDKLLTFIASDTCPLV (SEQ ID NO:25) and SGRRQRRFAGVVLAGVA (SEQ ID NO:26).
In a preferred embodiment of the present invention the composition comprises at least one peptide selected from the group consisting of SSKTQTHTQQDRPPQPS (SEQ ID NO:1); QPSTELEETRTSRARHS (SEQ ID NO:2); RHSTTSAQRSTHYDPRT (SEQ ID NO:3); PRTSDRPVSYTMNRTRS (SEQ ID NO:4); TRSRKQTSHRLKNIPVH (SEQ ID NO:5); SHQYLVIKLIPNASLIE (SEQ ID NO:6); IGTDNVHYKIMTRPSHQ (SEQ ID NO:7); YKIMTRPSHQYLVIKLI (SEQ ID NO:8); KLIPNASLIENCTKAEL (SEQ ID NO:9); AELGEYEKLLNSVLEPI (SEQ ID NO:10); KLLNSVLEPINQALTLM (SEQ ID NO:11); EPINQALTLMTKNVKPL (SEQ ID NO:12); FAGVVLAGVALGVATAA (SEQ ID NO:13); GVALGVATAAQITAGIA (SEQ ID NO:14); TAAQITAGIALHQSNLN (SEQ ID NO:15); GIALHQSNLNAQAIQSL (SEQ ID NO:16); NLNAQAIQSLRTSLEQS (SEQ ID NO:17); QSLRTSLEQSNKAIEEI (SEQ ID NO:18); EQSNKAIEEIREATQET (SEQ ID NO:19); TELLSIFGPSLRDPISA (SEQ ID NO:20); PRYIATNGYLISNFDES (SEQ ID NO:21); CIRGDTSSCARTLVSGT (SEQ ID NO:22); DESSCVFVSESAICSQN (SEQ ID NO:23); TSTIINQSPDKLLTFIA (SEQ ID NO:24); SPDKLLTFIASDTCPLV (SEQ ID NO:25) and SGRRQRRFAGVVLAGVA (SEQ ID NO:26).
It is further preferred that the composition further comprises at least one B cell epitope and/or at least one CTL epitope.
In yet another preferred embodiment the at least one B cell epitope and/or the at least one CTL epitope are linked to at least one of the T helper cell epitopes. It is also preferred that the composition comprises a plurality of epitope constructs in which each comprises at least one T helper cell epitope and at least one B cell epitope. Alternatively the composition may comprises a plurality of epitope constructs in which each comprises at least one T helper cell epitope and at least one CTL epitope.
It will be understood that the B cell epitope or CTL epitope may be any epitope. A currently preferred B cell epitope is an LHRH B cell epitope.
The composition of the present invention may comprises a plurality of T helper cell epitopes. These epitopes may be singular or be linked together to form a single polypeptide. It will be understood that where the epitopes are linked to together in a single polypeptide the epitopes may be contiguous or spaced apart by additional amino acids which are not themselves part of the T helper cell epitopes.
As discussed above in one embodiment the T helper cell epitopes and at least one B cell epitope and/or at least one CTL epitope in which the epitopes are linked. This may be done by simple covalent linkage of the peptides. In another embodiment the epitopes are polymerised, most preferably such as described in PCT/AU98/00076, the disclosure of which is incorporated herein by reference.
In yet another preferred embodiment the composition further comprises a pharmaceutically acceptable excipient, preferably an adjuvant.
In a further aspect the present invention consists in a method of inducing an immune response in an animal, the method comprising administering to the animal the composition of the second aspect of the present invention.
Pharmaceutically acceptable carriers or diluents include those used in compositions suitable for oral, rectal, nasal, topical (including buccal and sublingual), vaginal, parenteral (including subcutaneous, intramuscular, intravenous, intradermal, intrathecal and epidural) administration. They are non-toxic to recipients at the dosages and concentrations employed. Representative examples of pharmaceutically acceptable carriers or diluents include, but are not limited to water, isotonic solutions which are preferably buffered at a physiological pH (such as phosphate-buffered saline or Tris-buffered saline) and can also contain one or more of, mannitol, lactose, trehalose, dextrose, glycerol, ethanol or polypeptides (such as human serum albumin). The compositions may conveniently be presented in unit dosage form and may be prepared by any of the methods well known in the art of pharmacy.
As mentioned it is preferred that the composition includes an adjuvant. As will be understood an xe2x80x9cadjuvantxe2x80x9d means a composition comprised of one or more substances that enhances the immunogenicity and efficacy of a vaccine composition. Non-limiting examples of suitable adjuvants include squalane and squalene (or other oils of animal origin); block copolymers; detergents such as Tween(copyright)-80; Quil(copyright) A, mineral oils such as Drakeol or Marcol, vegetable oils such as peanut oil; Corynebacterium-derived adjuvants such as Corynebacterium parvum; Propionibocterium-derived adjuvants such as Propionibocterium acne; Mycobactenum bovis (Bacille Calmette and Guerin or BCG); interleukins such as interleukin 2 and interleukin 12; monokines such as interleukin 1; tumour necrosis factor; interferons such as gamma interferon; combinations such as saponin-aluminium hydroxide or Quil-A aluminium hydroxide; liposomes; ISCOM adjuvant; mycobacterial cell wall extract; synthetic glycopeptides such as muramyl dipeptides or other derivatives; Avridine; Lipid A derivatives; dextran sulfate; DEAE-Dextran or with aluminium phosphate; carboxypolymethylene such as Carbopolxe2x80x2 EMA; acrylic copolymer emulsions such as Neocryl A640 (e.g. U.S. Pat. No. 5,047,238); vaccinia or animal poxvirus proteins, sub-viral particle adjuvants such as cholera toxin, or mixtures thereof.
As will be recognised by those skilled in the art modifications may be made to the peptides of the present invention without complete abrogation of biological activity. These modifications include additions, deletions and substitutions, in particular conservative substitutions. It is intended that peptides including such modifications which do not result in complete loss of activity as T helper cell epitopes are within the scope of the present invention.
Whilst the concept of substitution is well known in the field the types of substitutions envisaged are set out below.
Another type of modification of the peptides envisaged include, but are not limited to, modifications to side chains, incorporation of unnatural amino acids and/or their derivatives during peptide synthesis and the use of crosslinkers and other methods which impose conformational constraints on the peptides.
Examples of side chain modifications contemplated by the present invention include, but are not limited to, modifications of amino groups such as by reductive alkylation by reaction with an aldehyde followed by reduction with NaBH4: amidation with methylacetimidate; acylation with acetic anhydride; carbamoylation of amino groups with cyanate; trinitrobenzylation of amino groups with 2,4,6-trinitrobenzene sulphonic acid (TNBS); acylation of amino groups with succinic anhydride and tetrahydrophthalic anhydride; and pyridoxylation of lysine with pyridoxal-5xe2x80x2-phosphate followed by reduction with NaBH4.
The guanidine group of arginine residues may be modified by the formation of heterocyclic condensation products with reagents such as 2,3-butanedione, phenylglyoxal and glyoxal.
The carboxyl group may be modified by carbodiimide activation via O-acylisourea formation followed by subsequent derivitisation, for example, to a corresponding amide.
Tryptophan residues may be modified by, for example, oxidation with N-bromosuccinimide or alkylation of the indole ring with 2-hydroxy-5-nitrobenzyl bromide or sulphenyl halides. Tyrosine residues on the other hand, may be altered by nitration with tetranitromethane to form 3-nitrotyrosine derivative.
Modification of the imidazole ring of a histidine residue may be accomplished by alkylation with iodoacetic acid derivatives or N-carbethoxylation with diethylpyrocarbonate.
Examples of incorporating unnatural amino acids and derivatives during peptide synthesis include, but are not limited to, use of norleucine, 4-amino butyric acid, 4-amino-3-hydroxy-5-phenylpentanoic acid, 6-aminohexanoic acid, t-butylglycine, norvaline, phenylglycine, ornithine. sarcosine, 4-amino-3-hydroxy-6-methylheptanoic acid; 2-thienyl alanine and/or D-isomers of amino acids.
The peptides of the present invention may be derived from CDV. Alternatively, the peptide or combination of peptide epitopes may be produced by recombinant DNA technology. It is, however, preferred that the peptides are produced synthetically using methods well known in the field. For example, the peptides may be synthesised using solution synthesis or solid phase synthesis as described, for example, in Chapter 9 entitled xe2x80x9cPeptide Synthesisxe2x80x9d by Atherton and Sheppard which is included in a publication entitled xe2x80x9cSynthetic Vaccinesxe2x80x9d edited by Nicholson and published by Blackwell Scientific Publications. Preferably a solid phase support is utilised which may be polystyrene gel beads wherein the polystyrene may be cross-linked with a small proportion of divinylbenzene (e.g. 1%) which is further swollen by lipophilic solvents such as dicliloromethane or more polar solvents such as dimethylformamide (DMF). The polystyrene may be functionalised with chloromethyl or aminomethyl groups. Alternatively, cross-linked and functionalised polydimethyl-acrylamide gel is used which may be highly solvated and swollen by DMF and other dipolar aprotic solvents. Other supports can be utilised based on polyethylene glycol which is usually grafted or otherwise attached to the surface of inert polystyrene beads. In a preferred form, use may be made of commercial solid supports or resins which are selected from PAL-PEG-PS, PAC-PEG-PS, KA, KR or TGR.
In solid state synthesis, use is made of reversible blocking groups which have the dual function of masking unwanted reactivity in the xcex1-amino, carboxy or side chain functional groups and of destroying the dipolar character of amino acids and peptides which render them inactive. Such functional groups can be selected from t-butyl esters of the structure RCOxe2x80x94OCMe3xe2x80x94CO. Use may also be made of the corresponding benzyl esters having the structure RCOxe2x80x94OCH2xe2x80x94C6H5 and urethanes having the structure C6H5CH2OCOxe2x80x94NHR which are known as the benzyloxycarbonyl or Z-derivatives and any Me3xe2x80x94COCOxe2x80x94NHR, which are known as t-butoxyl carbonyl, or Boc derivatives. Use may also be made of derivatives of fluorenyl methanol and especially the fluorenyl-methoxy carbonyl or Fmoc group. Each of these types of protecting group is capable of independent cleavage in the presence of one other so that frequent use is made, for example, of BOC-benzyl and Fmoc-tertiary butyl protection strategies.
Reference also should be made to a condensing agent to link the amino and carboxy groups of protected amino acids or peptides. This may be done by activating the carboxy group so that it reacts spontaneously with a free primary or secondary amine. Activated esters such as those derived from p-nitrophenol and pentafluorophenol may be used for this purpose. Their reactivity may be increased by addition of catalysts such as 1-hydroxybenzotriazole. Esters of triazine DHBT (as discussed on page 215-216 of the abovementioned Nicholson reference) also may be used. Other acylating species are formed in situ by treatment of the carboxylic acid (i.e. the N-alpha-protected amino acid or peptide) with a condensing reagent and are reacted immediately with the amino component (the carboxy or C-protected amino acid or peptide).
Dicyclohexylcarbodiimide, the BOP reagent (referred to on page 216 of the Nicholson reference), Oxe2x80x2Benzotriazole-N,N,Nxe2x80x2Nxe2x80x2-tetra methyl-uronium hexafluorophosphate (HBTU) and its analogous tetrafluoroborate are frequently used condensing agents.
The attachment of the first amino acid to the solid phase support may be carried out using BOC-amino acids in any suitable manner. In one method BOC amino acids are attached to chloromethyl resin by warming the triethyl ammonium salts with the resin. Fmoc-amino acids may be coupled to the p-alkoxybenzyl alcohol resin in similar manner. Alternatively, use may be made of various linkage agents or xe2x80x9chandlesxe2x80x9d to join the first amino acid to the resin. In this regard, p-hydroxymethyl phenylacetic acid linked to aminomethyl polystyrene may be used for this purpose.
Throughout this specification the word xe2x80x9ccomprisexe2x80x9d, or variations such as xe2x80x9ccomprisesxe2x80x9d or xe2x80x9ccomprisingxe2x80x9d, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
In order that the nature of the present invention may be more readily understood preferred forms there of will now be described with reference to the following non-limiting examples.